A light emitting diode (referred to as LED, hereinafter) has been recently changed from a light source for display into a light source for lighting LED to be expected as a next-generational energy saving light source and may replace an incandescent bulb or a fluorescent lamp. Therefore, technology innovations in the field of white LED technology, semiconductor lighting or a solid state lighting have been made in the worldwide.
In view of a light emitting mechanism of an LED, a light radiation basically depends on peculiar characteristics of a semiconductor and a fluorescent substance not on a heat or a discharged light. Because a LED lighting equipment does not feel hot unlike an incandescent bulb when it is touched, it is safe. Also, it generates less wastes because of its property that is longlasting. In addition, the LED lighting equipment does not include harmful materials such as fragile glass, mercury or organic material, therefore it is the earth environment-friendly light source for lighting. Therefore, the LED lighting equipment can be applied in various fields as well as in general lightings and is expected to form a huge market for the upcoming 10 years.
In general, a semiconductor light emitting diode is called a point source of light because of a small light emitting area of a LED and its property of going straight on. Accordingly, a lot of researches for obtaining a light emitting diode having a uniform and large divergence angle have been conducted. In general, a method of mixing inorganic and organic particles with an encapsulating material to be packaged or a method of widely spreading a light using a lens have been used. The former method is affirmatively used because it is benefical in saving the prime cost of a product and miniaturization.
As the prior art, a method to enlarge a divergence angle by dispersing light-conductive particles that scatter a light on the cover of a lamp is registered in U.S. Pat. No. 4,191,943 and a method to enlarge a divergence angle by dispersing inorganic particles such as CaF in the range of 6 to 25 wt % on an encapsulating layer is registered in U.S. Pat. No. 5,140,220.
By the way, an application about a method to use a light diffusing agent and a fluorescent substance altogether is pending. Nichia uses barium titanate, titanium oxide, aluminum oxide and silicone dioxide as diffusing agent for making a white color by mixing a blue wavelength lighting with a fluorescent substance in U.S. Pat. No. 6,069,440. As the similar technology, Arima Optoelectronics registered a technology using a fluorescent substance and bubbles in U.S. Pat. No. 6,614,170B2 and General Electric Company registered a technology of forming a diffusing layer separately from a fluorescent layer to diffuse a light emitted from a LED die in U.S. Pat. No. 6,653,765.
As described above, researches for widening a light diffusion range of a diode continue.